Sadly it's much easier to know when to sell after you've lost it all, I think. Selling those $0.0001 shares at $0.05+ is a no brainer in hindsight, but at the time you can get sucked into the hype and think "this is just a million, if it goes to $0.15 then I'll have three million!
Or sometimes you just see any criticism of Sharp as a personal attack and dig in more and more, stubbornly holding through $1M+ losses as the price crashes.
I don't know many who claim to have actually kept the millions they "made," hopefully those are the ones that are no longer on the forums pumping.